Coated paper and method of making the same



Patented June 21, 1932 ARLIE W. SCHORGER, F MADISON, WISCONSIN,ASSIGNOR, BY MESNE ASSIGNMENTS,

FREEPORT, ILLINOIS, A CORPORATION OF TO BURGESS CELLULOSE COMPANY, OFDELAWARE TED STATES PATENT OFFICE;

Y COATED PAPER AND METHOD OF MAKING THE No Drawing. Continuation ofapplication Serial No. 335,390, filed January 26, 1929. This applicationfiled November 12, 1929. Serial No. 406,724.

This invention relates to a coating for paper and especially stereotypemats.

This application is a continuation of my copending application SerialNo. 335,390, filed January 26, 1929.

The objects of my invention are to produce a smooth surface so that finecuts reproduce well; to bind the surface fibers together so that theywill not be loosened by mechanical action as when stereotype plates"areremoved; and to facilitate release of metal after stereotype metaliscast. Although my coating is especially useful for stereotype mats, itmay also be applied to other paper or fibrous products.

Various coatings have been used for stereotype mats but none have provedentirely satisfactory. I have discovered that a coating will possesssuperior qualitiesif it contains certain ingredients which have not beenused heretofore to the best of my knowledge. My preferred formulacomprises a water solution or suspension which includes thin boilingstarch, yellow dextrin, clay, bentonite, a salt of a higher fatty acid,and a preservative, such as otassium chromate,

but I believe that the atty acid salt is the ing and the surface alsobecomes too' dense i and hard. As examples of fatty'acids salts may bementioned the caustic alkali, alkaline earth, and heavy metal salts ofpalmitic, stearic, oleic acids, etc. The saltsof'the individual acidsmay be used, or their mixtures. The salts of the higher fatty acids maybe used also admixedwith the metallic salts of abietic and similar resinacids. The. term fatty acid salt will be used to include any one of thesalts mentioned above or their mixtures, and is not confined to thefatty acids mentioned. V

The following preferred formula may be boiling starch de ending onfluidit varied over a considerable range to suit the specificrequirements of the user:

Thin boiling starch 2 lbs.

Yellow dextrin 4 lbs.

Clay (kaolin) 7. 5 lbs.

Bentonite 5 lbs.

Salt of a higher fatty acid odium stearate') 325 lbs. (0.1-0.5 lbs.)

Potassium chromate 70 grams Water 11 gallons All the constituents exceptthe fatty acid salt are mixed thoroughly in the dry condition so thatthe finished "product will be" free from lumps of bentonite. Add gallonsof water and boil until the suspension does not increase in thickness.Actual boiling for 15minutes is usually'ample. A soluble fatty acid saltsuch as sodium stearate is dissolved in 1 gallon of hot water, and thetwo solutions after some cooling are mixed thoroughly. The coatingsolution has a consistency approximating that of a paint. The coatingwhen cold is applied to the paper or mats by means of a brush or coatingmachine. The fatty acid salt'is preferably kept below 1% (dry fattyacid) of the total mixture.

The yellow dextrin is used on account of its low viscosity since thelatter permits it to penetrate the surface of the mat and bind thefibers together. It is preferred over the white dextrin which is moregummy and possessed of low penetrability. The percentage of yellowdextrin may vary preferably from '3 to 5 percent of the coating mixture.1 also believe that the use of yellow dextrin in stereotype mat coatingsis novel. 7

,. The starch has 'a'high viscosity and low penetrating power. It givesbody to the coating and cements'the clay together. The percentage mayvary over a considerable range. Thin boiling starch is prepared byheating starch with small amount of acid or oxidizing agent at 100 F.There is a partial hydrolysis of the starch without bursting ofgranules. It is sold as 20, 30, 60, thin after boiling. White extrin ispractica ly .90 thin boiling starch.

Clay such'as kaolin is used for the purl pose of filling the depressionsin the paper or stereotype mat and producing a smooth surface. 'Theamount may vary drated considerably. 'Bentonite, a colloidal cla is usedfor two purposes-to give body to t e coating so that t will not settlereadily; and when used on vent molding by fungi. Other chemicals,'

ing and cooling of the constituents,

.rapid stirring,

such as sodium benzoate or boric acid may be used for that purpose.

If it is desired to use the insoluble salts of the alkali earths andheavy metals a solution of the alkali metal salts of the fatty acids,such as sodium oleate, sodium-stearate, etc. ma be treated with a saltof the desired meta suc as zinc sulfate, magnesium sulfate, alum,calcium chloride, etc., as is well known to those skilled in the art.The precipitation is performed-preferably after mixing, heatusing inorder that the insoluble fatty acid salt formed will be finely anduniformly distributed. a

For stereotype mats bentonite or its equivalent should be used in thecoating. For paper other than mats the bentonite or its neeava prisingan insoluble salt of a higher fatty acid and bentonite.

10. A stereotype mat having a surface coating of a mixture containing'asalt of a higher fatty acid in an amount of less than 5 percent (drybasis) of the solid ingredients ofsald coating.

of a higher fatty acid and-bentonite in suit-. h I

able proportions for use as a coating on the impression surface of astereotype mat.

tonite in suitable proportions for use as a coating on the impressionsurface of a stereotype mat. 4

. n testimony whereof I aflix m signature. ARLIE W. SC ORGEB.

equivalent may be replaced entirely or in part by clay in addition tothe clay specified. I claim: 1. Themethodofmakin a pervious surface on astereot mat whi comprises facing the mat wit a water suspensioncontaining a salt of a higher fatty acid and ahydrate mineral whichloses its water on scorching, and then scorchin the mat.

2. The method 0 making a-pervious surface on a stereotype matwhich-comprises fac-. ing the mat with a water sus nsion containing asalt of a hi her fatty acid and bentonite, and then scorc ing the .mat.

3. A stereoty prising a salt 0 a low dextrin.

4. A stereotype mat having a coating comprising a salt of a higher fattyacid, yellow dextrin, a thin boiling starch, clay, and a pre--servative. v

5. A stereotype mat having a coating containing'yellow dextrin as one ofthe ingredients.

6. A stereotype mat having 'a coating comprising asalt of a higherfatty. acid, yellow higher fatty acid and yeldextrine-and thin boilingstarch.

7. 'A stereotype mat having a coating com. prising a salt of a higherfatty acid, yellow dextrin and clay.

8. A stereotype mat having a coating comrising" a salt of a ntonite.

9. A stereotype mat having a coating commat having a coating coinhigherfatty acid and 13. A coating solution comprisingan in- I soluble salt ofa higher-fatty acid and benico I Ill lac

